Tested permethrin (pyrethroid), endosulfan (cyclodiene), methomyl (carbamate), methamidophos (organophosphate) and Bacillus thuringiensis. At the LC90, resistance ratios were 13 for permethrin and 145 for methamidophos. This is the first documented occurrence of resistance to synthetic insecticides in North American Plutella xylostella larval populations. -from Authors